1. Field of the Invention
The present invention relates to a fuel injection control system for an internal combustion engine and more particularly to a control system for improving the starting performance of an internal combustion engine.
2. Description of Related Art
Conventionally, it is known to inject a relatively large amount of fuel at a timing which is not synchronous with a suction stroke, as a fuel injection control carried out when an internal combustion engine is started. Fuel evaporated before the suction stroke is sucked into cylinders and is burned, thereby starting the internal combustion engine. By increasing the fuel injection amount, the fuel (fuel evaporated and sucked into the cylinders) necessary for the start-up is assured.
It is also known, because the evaporation amount of fuel changes depending on the engine temperature (cooling water temperature), to correct the fuel injection amount at the time of starting in accordance with the cooling water temperature.
Further, Japanese Examined utility Model Publication No. 1-21156 proposes it is known to improve the starting performance of an internal combustion engine, to learn the relation between the fuel injection amount at the time of engine starting and a time actually required for start-up, and to increase or decrease the fuel injection amount at the time of the next engine starting, on the basis of the learned result, so as to reduce the starting.
At the time of so-called cold engine starting which is a start-up when the engine temperature is low, however, an evaporation amount of fuel is small and even if the fuel injection amount is increased, and a misfire occurs. There is consequently a problem that exhaust emission gets worse.